Assigning unknown species names to ambiguous populations in the US Potato Genebank

Authors: Ames Sevillano, Mercedes; Fenstemaker, Sean; DEL RIO, ALFONSO - University Of Wisconsin; Bamberg, John

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2025
Publication Date: 2/13/2025
Citation: Ames Sevillano, M.I., Fenstemaker, S.M., Del Rio, A., Bamberg, J.B. 2025. Assigning unknown species names to ambiguous populations in the US Potato Genebank. American Journal of Potato Research. 1-6 (2025). https://doi.org/10.1007/s12230-025-09983-9.
DOI: https://doi.org/10.1007/s12230-025-09983-9

Interpretive Summary: The US Potato Genebank (USPG) has germplasm of a single crop, about 6,500 samples of tuber-bearing Solanum species. Despite many years of vigorous taxonomic efforts, 80 populations at USPG were indexed only as “Solanum spp.” as of 2023, suggesting that the exact species name was unknown. DNA markers were used to match these populations to an array of standard species. Populations were also grown to maturity in the field and determined using the latest taxonomic keys. Species determinations based on the closest DNA match were highly supported by existing records for ploidy and country of origin but only modestly by taxonomic keys (36%). The new species name assignments are now documented in USPG’s online database in the Germplasm Resources Information Network (GRIN). Giving these genebank resources the species name that is the best fit according to DNA provides a practical platform for deploying them for research and breeding.

Technical Abstract: USDA maintains a national network of wild and cultivated relatives of crops to support breeding. The site for potato is the US Potato Genebank (USPG) at Sturgeon Bay, Wisconsin. USPG has about 6,500 samples of nearly 100 Solanum species related to the commercial potato. Despite many years of effort on taxonomic classification, in 2022 there were still about 80 samples to which no satisfactory species name has been assigned because the plants were somewhat ambiguous in appearance or records. We undertook a systematic study of these "unknown" seedlot, planting them for observation, sampling and assessing DNA, and using taxonomic keys to come to the best approximation of how these should be classified. These unknowns were also compared to a set of standard "known" species. Use of taxonomic keys or physical observations were not as conclusive as similarly of DNA markers. Assigning the "unknown" sample the species name of the most similar known species according to DNA provided a lot of useful information. Now the number of chromosomes, expected breeding behavior, and useful traits associated with the new names takes these unknowns out of "limbo" and makes them more useful to researchers and breeders who wish to use USPG stocks.